Representatives from nearly 200 countries agreed at the COP28 climate summit on Wednesday to begin reducing global consumption of fossil fuels to avert the worst of climate change, signalling the eventual end of the oil age.

The deal struck in Dubai after two weeks of hard-fought negotiations was meant to send a powerful message to investors and policy-makers that the world is united in its desire to break with fossil fuels, something scientists say is the last best hope to stave off climate catastrophe.

COP28 President Sultan al-Jaber called the deal "historic" but added that its true success would be in its implementation.

"We are what we do, not what we say," he told the crowded plenary at the summit. "We must take the steps necessary to turn this agreement into tangible actions."

Several countries cheered the deal for accomplishing something that until now eluded decades of climate talks.

"It is the first time that the world unites around such a clear text on the need to transition away from fossil fuels," Norway's Minister of Foreign Affairs Espen Barth Eide said.

More than 100 countries had lobbied hard for strong language in the COP28 agreement to "phase out" oil, gas and coal use, but came up against powerful opposition from the Saudi Arabia-led oil producer group OPEC, which said the world can cut emissions without shunning specific fuels.

That battle pushed the summit a full day into overtime on Wednesday, and had some observers worried the negotiations would end at an impasse.

Members of the Organization of the Petroleum Exporting Countries control nearly 80% of the world's proven oil reserves along with about a third of global oil output, and their governments rely heavily on those revenues.

Small climate-vulnerable island states, meanwhile, were among the most vocal supporters of language to phase out fossil fuels and had the backing of major oil and gas producers such as the United States, Canada and Norway, as well as the European Union and scores of other governments.

"This is a moment where multilateralism has actually come together and people have taken individual interests and attempted to define the common good," U.S. climate envoy John Kerry said after the deal was adopted.

The lead negotiator for the Alliance of Small Island States, Anne Rasmussen, criticised the deal as unambitious.

"We have made an incremental advancement over business as usual, when what we really need is an exponential step change in our actions," she said.

But she did not formally object to the pact, and her speech drew a standing ovation that lasted nearly two minutes.

Danish Minister for Climate and Energy Dan Jorgensen marvelled at the circumstances of the deal: "We're standing here in an oil country, surrounded by oil countries, and we made the decision saying let's move away from oil and gas."

EMISSIONS REDUCTION

Members of the Organization of the Petroleum Exporting Countries control nearly 80% of the world's proven oil reserves along with about a third of global oil output, and their governments rely heavily on those revenues.

Small climate-vulnerable island states, meanwhile, were among the most vocal supporters of language to phase out fossil fuels and had the backing of major oil and gas producers such as the United States, Canada and Norway, as well as the European Union and scores of other governments.

"This is a moment where multilateralism has actually come together and people have taken individual interests and attempted to define the common good," U.S. climate envoy John Kerry said after the deal was adopted.

The lead negotiator for the Alliance of Small Island States, Anne Rasmussen, criticised the deal as unambitious.

"We have made an incremental advancement over business as usual, when what we really need is an exponential step change in our actions," she said.

But she did not formally object to the pact, and her speech drew a standing ovation that lasted nearly two minutes.

Danish Minister for Climate and Energy Dan Jorgensen marvelled at the circumstances of the deal: "We're standing here in an oil country, surrounded by oil countries, and we made the decision saying let's move away from oil and gas."